Numerical simulation of upwelling currents in pockmarks,and data from the Inner Oslofjord,Norway |
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Authors: | Øyvind Hammer Karen E Webb Davy Depreiter |
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Institution: | (1) Physics of Geological Processes, University of Oslo, P.O. Box 1048, Blindern, 0316 Oslo, Norway;(2) Renard Centre of Marine Geology, University of Gent, 9000 Gent, Belgium |
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Abstract: | The deflection of oceanic or tidal currents into pockmarks has been studied by both general three-dimensional computational
fluid dynamics simulations and acoustic measurements in a number of pockmarks in the Inner Oslofjord, Norway. The modeling
demonstrates upstream convergence of flow lines, followed by upwelling over the pockmark. This upwelling is an effect of deflected
regional currents, not of expulsion of fluids or gas from the seafloor, and is sufficiently strong to prevent the settling
of fine particles. The field measurements, although noisy at low vertical velocities, are consistent with the hypothesis of
upwelling. The reduction in sedimentation rate inferred over the pockmarks (relative to that of the flat surrounding seabed)
can explain the maintenance, or even deepening of pockmarks in the absence of fluid or gas seepage. The current pattern may
also have consequences for the marine biology of pockmarks. |
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Keywords: | |
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